Don't know about the dial-up as I have cable modem but the pop-up stopper included in Mozilla works perfectly on the version I downloaded. I even uninstalled the pop-up stopper I was using since it is no longer needed.
Well, I called again today and ranted at the phone company. Seems my dsl modem was somehow "lost" in the system (in other words, some moron forgot to dispatch the order on it). They said they are going to overnight it and that I would have it tomorrow. I'll believe it when I see it. I might try Mozilla Firefox (the version I have) again then. I do like the features on it, and I really didn't have any problem with it until I had the dialup. I wasn't using the Mozilla popup stopper. I also couldn't make my Yahoo companion toolbar work with Mozilla, but I can live with that since it has the customized buttons at the the top.